This disclosure generally relates to techniques for forming plastic products and in particular, relates to techniques for fabricating interior panels for aircraft.
Vacuum forming is a thermoforming process that enables molding a heated and softened sheet of thermoplastic material by applying vacuum suction through a perforated/vented mold. The suction makes the sheet stretch and drape over the mold surface to take the form of the mold shape. The sheet is then cooled down to solidify and retain the shape of the mold. Sometimes the cooling is aided using blown cooling air.
Twin-sheet vacuum thermoforming is a thermoforming process that refers to the molding of a first sheet in an upper mold and a second sheet in a lower mold, followed by an operation of compression of the two formed sheets against each other while still hot and relatively soft, thereby providing a fused interface to produce a hollow type product.
Although twin-sheet vacuum thermoforming has been successfully used for decades to manufacture hollow products such as gas tanks, ducts, pallets, and water craft, for example, it has been found desirable to further provide products with inserts to improve the structure and/or certain properties of the product. An insert can be defined as a body that is not subjected to molding and which has to be inserted between the molded sheets and generally within a cavity created inside the thermoformed hollow product.
The fabrication of molded aircraft components from thermoset composite materials is well known in the art. However, the current materials and fabrication methods for fabricating sidewall and ceiling panels for aircraft suffer from very long fabrication cycle-time, material waste and disposal cost, and involve numerous processing cycles with individually fabricated components converted to sub-assembles and manually assembled at a significant cost and weight that retain product deficiencies and waste. The current process also requires multiple complex tools and equipment, which require long lead times, storage facilities and infrastructure. Custom treatments of composite panels are also required to address thermal and noise generated by airflow, equipment and other systems. The current processes do not allow for the integration of new decorative texture uniformity that is required by complex design configurations. The current process is also not tool-side controlled, which affords part-to-part variability and requires repairs.
Existing composite constructions often contain multiple materials that exhibit only a small difference in their thermal properties. However, the processing methods that utilize a uniform temperature field to fabricate these existing composite configurations are not optimal for many new materials or material configurations that exhibit highly variable thermal properties. While production of composite structures using these new materials may still be feasible using a multiple-stage processing method, it is also inefficient in both time and energy. Single-stage processing is preferred for its efficiency.
Current conventional tooling and fabrication methods also lack the capability to fabricate net size parts. This results in excessive material trim-off from the part periphery and internal cut-outs. In addition to material waste, the added steps of cutting induces residual stresses and embrittlement that can adversely affect the service life of the component. Thus, a net shape part that does not require tools to remove waste material from the part will be a significant benefit.
There is a need for panel fabrication processes that avoid the above-stated disadvantages and impart additional improvements.